Investigation of Neutral Axis Shifting in Rotary Draw Bending Processes for Tubes



Rotary draw bending is one of the most important methods used for tube forming processes. During the process of tube bending, the neutral axis of the tube moves toward the inner arc. The wall thickness distribution changes for the tube's cross section. Thinning takes place in the outer arc of the tube, whereas thickening occurs in the inner arc of the tube. In this paper, a geometrical model is presented to calculate the neutral axis shifting for different bending angles. The finite element simulation is used to predict the results close to the geometrical model results. In addition, the effect of the different materials (Al alloy 6009 and stainless steel alloy 1.4301) on the rotary draw bending process is compared. Finally, the results of the distributions of the axial strain and wall thickness of the bend are obtained.